The invention relates to a system for operating pipeline tools, in particular expansion and pull heads with a rod assembly that is rigid when pushed. These pipeline tools are known to be used for rehabilitating pipelines, exchanging pipes, or constructing new pipelines.
When pipeline pipes are horizontally exchanged, pipeline tools such as expansion and pull heads are moved through the pipeline, whereby old pipes are broken up and pushed aside or pulled out of the pipeline. At the same time, new pipes can be inserted into the pipeline. Various systems are known to move the tools with the forces required for this purpose. For example, pull ropes pull the tools through the pipeline with the assistance of hoist gear. To avoid installation of such hoist gear in the pipeline axis, the hoist gear can be operated above ground by redirecting the pull rope out of the pipeline axis via a pulley. However, hoist gear is expensive and restricted to application of pull forces.
Higher forces can be applied via hydraulic linear drives. These too can be driven by a rope; however, they are then also restricted to pull forces.
To apply push forces and higher pull forces, linear drives, which are operated by rod assemblies that are rigid when pushed, are described in, for example, DE 196 08 980 C2. For this purpose, the linear drive is arranged in a hopper or pit in the pipeline axis.
In operation, the individual rod assembly sections must be strung together or connected to each other. Consequently, for longer bores, the rod assembly includes numerous rod assembly sections which must be, in accordance with the progress of the boring, connected to or separated from each other, one at a time. An individual section is of limited length and must be very short particularly when the boring takes place in a short building pit, for example an inspection chamber. These can have diameters of, in part, less than one meter. This means that connecting the rod segments is considerably cumbersome, in particular in the case of long bore lengths. The presence of human beings in the vicinity of the drive for connecting the rod segments is particularly undesirable if it must take place in a narrow and often-times a foul-smelling inspection chamber, as is frequently the case when rehabilitating pipelines.
The prior art discloses efforts to simplify connection of the rod segments by providing, for example, couplings instead of screw connections.
Such a rod assembly is known from DE 199 18 530 A1. In order to facilitate a highly tensile or rotationally fixed connection between two rod assembly sections, these couplings have an axially protruding lug-like attachment piece at the front end of the rod assembly section to be coupled. This attachment piece glidingly engages the back end of preceding rod assembly section.
As an alternative solution approach, DE 196 08 980 describes a sprocket chain by means of which push and pull forces can be applied to a pipeline tool so that it is unnecessary to connect rod assembly sections in the pit, while pull forces can still be applied. However, such a chain is expensive, fragile, and difficult to transport.
Newer developments have resulted in rod assemblies that further simplify connecting the rod assembly sections and that even allow for connecting the rod assembly sections on the earth's surface. Thus, an extended presence in the pit is unnecessary. DE 100 65 533 A1 describes a coupling by means of which rod assembly sections are plugged together through connecting corresponding ends of the rod assembly sections. This is accomplished by shifting the rod assembly section axes in parallel fashion. Thereby, a first rod assembly section has a journal which engages a corresponding recess of a second rod assembly section. In this way, the rod assembly section can already be connected on the earth's surface so that, once the linear drive has been installed in the pit and the rod assembly has been assembled, operation can be performed from the earth's surface for a certain time period.